Control system for pneumatic thread aligner

ABSTRACT

This disclosure relates to the controlling of the air stream of a pneumatic device for aligning threads or chains of threads of a sewing machine. The control device includes a first switch actuated in response to machine operation to energize the circuit and a second switch responsive to the position of material being sewn operative to energize the circuit only when the material being sewn is in a predetermined position whereby the flow of air is held to a minimum, primarily only at the start of a sewing operation and after sewing of the material has discontinued but not until after the actuation of the thread cutter.

United States Patent [19-] Daniel et a1. 1

[ 'Apr. 9, 1974 [73] A ssignee: Union Special Maschinenfabrik,

G.m.b.H., Stuttgart, Germany 221 Filed: Sept. 26, 1972 21 App]. No.: 292,326

[30] Foreign Application Priority Data Oct. 9, 1971 Germany 2150459 [52] US. Cl. 112/252, l12/D1G. 1 [51] Int. Cl D05b 65/04 [58] Field of Search 112/2, 121.11, 121.15,

112/121.26, 129, 130, 252, DIG. l

[56] References Cited UNITED STATES PATENTS 3,149,594 '9/1964 Buckreus et a1. 112/252 3,490,403 l/1970 Boucraut 112/252 2,418,356 4/1947 Kleber 112/252 UX 3,125,052 3/1963 Spivey 112/252 3,217,680 11/1965 Harris, Jr. et al 112/252 3,548,768 12/1970 Juenemann et a1 112/252 3,582,663 6/197] Troast, .lr 112/252 X 3,698,336 10/1972 Launer 112/252 Primary Examiner-Werner H. Schroeder Attorney, Agent, or Firm-Diller, Brown, Ramik & Wight [5 7] ABSTRACT This disclosure relates to the controlling of the air stream of a pneumatic device for aligning threads or chains of threads of a sewing machine. The control device includes a first switch actuated in response to machine operation to energize the circuit and a second switch responsive to the position of material being sewn operative to energize the circuit only when the material being sewn is in a predetermined position whereby the flow of air is held to a minimum, primarily only at the start of a sewing operation and after sewing of the material has discontinued but not until after the actuation of the thread cutter.

10 Claims, 2 Drawing Figures CONTROL SYSTEM FOR PNEUMATIC THREAD 1 ALIGNER BACKGROUND OF THE INVENTION In the case of sewing machines with cutting arrangement for cutting of threads or chains of threads it has become known to align the threads or chains of threads by means of air, in relation to the blades of the cutter, and to carry them away after cutting, such as shown for example in U; S. Pat. No. 3,143,987. In order to decrease the consumption of air and thus the costs for the production of compressed air or of a vacuum, it has already become known to turn off automatically the air stream while the machine is at standstill. For this purpose, as a rule, valves are used which are turned on and off with starting and stopping of the sewing machine, for example, valves which are located in the draw rod mechanism between the pedal andthe coupling lever.

With this heretofore known control arrangement, it is true that the air stream is interrupted during standstill of the machine, but in the case of relatively long seams, the consumption of air is still nevertheless relatively considerable. A substantial disadvantage of'this heretofore known control arrangement is that the deceleration of the machine, after the machine is turned off, is not taken into account. The air stream no longer seizes the threads or chains of threads which pile up during deceleration of the machine, as a result of which the cutter becomes clogged.

SUMMARY OF THE INVENTION The present invention is based on the objective of achieving with relatively small expenditure a further saving in air and, beyond that, of preventing the pile upof threads or chains of thread during deceleration of the machine in the case of a control arrangement for the air stream for the pneumatic arrangement of threads or chains of threads to a cutter in the case of sewing machines with a switch for the turning on and off of the stream of air controlled in dependence upon the running of the machine.

This objective is achieved through the fact that a switch controlled by the sewing material is coupled with the switch controlled in dependence on the running of the machine with the two switches preferably disposed in series. Another characteristic of the control system is that a delay element is connected following the two switches.

In a preferred embodiment of the invention a photoelectric switch is-provided in a conventional control arrangement having a switch that turns on a solenoid valve when the sewing machine is started. The light barrier of the photoelectric switch lies in the direction of sewing behind the place for formation of the stitch, approximately at the level of the inlet opening of the cutter.

Further details of thepreferred embodiment include a double H-NAND gate connected in series with the switches and a capacitor for the delay of the drop off of the solenoid valve is connected to the double l-l- NAND gate. I

With the control arrangement according to the present invention, the air stream is not only interrupted during standstill of the machine, but also during sewing. The air stream is released only when the machine binds off. As soon as the beginning of the sewing material has passed the place for formation of the stitch, the air stream is turned off automatically and air starts to flow again only when the end of the sewing material leaves the place for formation of the stitch. Furthermore, the delay member prevents a piling up of threads or thread chains during decleration of the machine. These advantages are achieved with a relatively simple, inexpensive control arrangement. The control arrangement moreover offers a further possibility, which resides in the fact that it is provided with a switch element to run the cutter on and off. This switch element preferably receives the control impulses of the solenoid valve.

. By turning the cutter on only at those times at which it is needed, the wear and tear of the cutter can be considerably decreased and particularly advantageously a separate drive can be used for the blades. This advantage is achieved without any special expenditure whenever the control impulse for the air is used for control of the cutter.

With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims and the several views illustrated in the accompanying drawings: In the drawings:

FIG. 1 is a front elevational view of a sewing machine with table and motor.

FIG. 2 is a circuit diagram of a control arrangement.

In the embodiment shown by way of example an overlock sewing machine 1 is driven by a motor 2 having a clutch controlled by a pedal 3. Another pedal 4 serves to lift the presser foot and is connected with a control rod system, not shown, by way of a chain 5. Pedal 3 is connected by way of a chain 6 with a control lever 7 of the clutch of motor 2.

Control pedal 3 is further connected with a switch 9 by way of the chain 6 and an intermediate spring 8. This switch 9 is connected with a switch box 12 by way of a cable 11 from which a cable 13 leads to a solenoid valve 14. Another cable 15 leads from switch box 12 to a main switch 16. Furthermore, an air conduit 17 leads to the solenoid valve 14 and another air conduit 18 leads from the solenoid valve to a cutter for cutting the thread chains, which cutter has not been shown.

According to the present invention, a photoconductive cell together with a light source is disposed in a housing 19 on the overlock sewing machine 1. The ray of light of the source of light is directed toward a reflector (not shown) which lies behind the place for formation of the stitch approximately at the level of the inlet opening of the cutter and is reflected back onto the photoconductive cell.

In the circuit diagram of FIG. 2, the photoconductive cell designated by 21 precedes switch 9. As long as the ray of light strikes photoconductive cell 21, current flows through the transistor 22, as a result of which transistor 23 is blocked. Thus, current flows through cable 24 to switch 9.

When switch 9 is open, the current flows through cable 25 to the outlet of the gate 26. As a result of that, transistor 27 remains blocked and solenoid valve 14 is switched off.

When starting to sew, switch 9 is automatically closed with engagement of the clutch of motor 2 and thus with the start of sewing machine 1. The sewing material which still is located in front of the point for formation of the stitch does not yet cover up the reflectors, so that the ray of light strikes the photoconductive cell 21. Thus, transistor 22 is driven and transistor 23 is blocked. The current passing through cable 24 flows by way of switch 9 to gate 26. Thus, the supply of current from cable 25 to gate 26 is blocked and this current flows from cable 25 to transistor 27. Transistor 27 connects through and solenoid valve 14 opens. After the leading edge of the sewing material has passed the reflector and darkened the photoconductive cell 21, transistor 22 no longer receives control current and blocks. The current from cable 28 flows through transistor 23 which opens and allows the current to flow from cable 24.

As a result of that, the inlet of gate 26 is connected by way of transistor 23 and cable 31 with zero and at its outlet draws current from cable 25. As a result of that, transistor 27 blocks and solenoid valve 14 is turned off. Switch 9 can be opened and closed as often as desired until completion of the seam, i.e., the machine can be stopped as often as desired without there being any change occurring in the state of gate 26 and without the solenoid valve being turned on again.

As soon as the end of the sewing material again releases the ray of light to the photoconductive cell 21, current flows from cable 24 via the still closed switch 9 to the inlet of gate 26. This causes a flow of current from cable 25 through transistor 27 and the energization of solenoid valve 14. The solenoid valve 14 stays energized as long as the machine binds off, i.e., until switch 9 is opened. With the opening of switch 9, the clutch of motor is released and the machine is turned off. The solenoid valve 14, however, is still being kept energized by way of capacitor 29 for a certain period of time corresponding to the deceleration of the machine. After switch 9 is opened, the capacitor 29 reverses the charge and blocks the current supply from cable 25 to gate 26 during the time of charge reversal.

A cable 32 which leads to a transistor 33 is branched off from transistor 27. Transistor 33 serves to control cutter 34 or its drive. In the embodiment shown by way of example, transistor 33 receives a control impulse simultaneously with transistor 27. Therefore, the cutter operates only at the beginning and end of a sewing process whenever the air stream also is turned on.

Within the scope of the present invention, it naturally is possible to provide an electric key switch instead of photoconductive cell 21. Also, switch 9 could be connected with the photoelectric switch which is controlled by the edge of the sewing material and which turns the sewing machine on and off. Finally, it also is possible to replace the electric switching and control members by pneumatic members.

We claim:

1. In a sewing machine of the type having a control device for controlling the operation thereof, a thread cutter, an air stream device for pneumatic alignment of threads or chains of threads relative to said cutter, and a switch actuated control device for said air stream device operable in accordance with the operation of the sewing machine to effect an air flow; a control arrangement including further switch means controllable by the position of material being sewn, said further switch means being operable to override said switch to prevent said air flow.

2. A control arrangement according to claim 1 wherein said switch and said switch means are in series.

3. A control arrangement according to claim 2 together with a delay device defining a holding system relative to said switch.

4. A control arrangement according to claim 1 wherein said switch means is a photoelectric switch.

5. A control arrangement according to claim 4 wherein said photoelectric switch has operatively associated therewith a light barrier traversing the path of material being sewn and generally aligned with said cutter.

6. A control arrangement according to claim 1 wherein a switching device is coupled with said switch and said switch means, said switching device being in the form of a double H-NAND gate.

7. A control arrangement according to claim 6 wherein a time delay device is operatively associated with said double H-NAND gate.

8. A control arrangement according to claim 6 wherein a time delay device is operatively associated with said double H-NAND gate, said delay device including a capacitor.

9. A control arrangement according to claim 1 together with a switching member for controlling the operation of said cutter.

10. A control arrangement according to claim 1 together with a switching member for controlling the operation of said cutter, and means for operating said switching member in unison with the operation of said air stream control device. 

1. In a sewing machine of the type having a control device for controlling the operation thereof, a thread cutter, an air stream device for pneumatic alignment of threads or chains of threads relative to said cutter, and a switch actuated control device for said air stream device operable in accordance with the operation of the sewing machine to effect an air flow; a control arrangement including further switch means controllable by the position of material being sewn, said further switch means being operable to override said switch to prevent said air flow.
 2. A control arrangement according to claim 1 wherein said switch and said switch means are in series.
 3. A control arrangement according to claim 2 together with a delay device defining a holding system relative to said switch.
 4. A control arrangement according to claim 1 wherein said switch means is a photoelectric switch.
 5. A control arrangement according to claim 4 wherein said photoelectric switch has operatively associated therewith a light barrier traversing the path of material being sewn and generally aligned with said cutter.
 6. A control arrangement according to claim 1 wherein a switching device is coupled with said switch and said switch means, said switching device being in the form of a double H-NAND gate.
 7. A control arrangement according to claim 6 wherein a time delay device is operatively associated with said double H-NAND gate.
 8. A control arrangement according to claim 6 wherein a time delay device is operatively associated with said double H-NAND gate, said delay device including a capacitor.
 9. A control arrangement according to claim 1 together with a switching member for controlling the operation of said cutter.
 10. A control arrangement according to claim 1 together with a switching member for controlling the operation of said cutter, and means for operating said switching member in unison with the operation of said air stream control device. 